"clang" related error while compiling Radiance on Mac

Hi, List,

I got the following "clang" related error message while compiling Radiance4
on Mac:

···

####################################################################
Current rmake command is:
#!/bin/sh
exec make "SPECIAL=ogl" \
    "OPT=-O2" \
    "MACH=-DBSD -DNOSTEREO -Dfreebsd -I/usr/X11R6/include -L/usr/X11R6/lib"
\
    ARCH=Intel "COMPAT=" \
    INSTDIR=/Applications/Radiance/HEAD_2012_06_23/ray/bin \
    LIBDIR=/Applications/Radiance/HEAD_2012_06_23/ray/lib \
    ESUFFIX= \
    CC=cc CONFIGURE_ARCH=i386 "$@" -f Rmakefile
Do you want to change it? n
Making programs...
/Applications/Radiance/HEAD_2012_06_23/ray/src/common
/Applications/Radiance/HEAD_2012_06_23/ray/src
In directory common...
cc -DBSD -DNOSTEREO -Dfreebsd -I/usr/X11R6/include -L/usr/X11R6/lib -O2
-c -o cone.o cone.c
clang: warning: argument unused during compilation: '-L/usr/X11R6/lib'
......
cc -DBSD -DNOSTEREO -Dfreebsd -I/usr/X11R6/include -L/usr/X11R6/lib -O2
-c -o bsdf.o bsdf.c
clang: warning: argument unused during compilation: '-L/usr/X11R6/lib'
bsdf.c:1432:2: warning: implicit declaration of function 'multisamp' is
invalid
      in C99 [-Wimplicit-function-declaration]
        multisamp(pert, 3, rv);
        ^
1 warning generated.
......
####################################################################

Have I missed sth critical here?

(Mac OSX 10.7.4 with Xcode.4.3.2)

- Cheers, Ji